Posted on by John Williams

A Colorful and Unexpected Reversal at Titan

This artist’s impression of Saturn’s moon Titan shows the change in observed atmospheric effects before, during and after equinox in 2009. The Titan globes also provide an impression of the detached haze layer that extends all around the moon (blue). This image was inspired by data from NASA’s Cassini mission. Image Credit: ESA

A certain slant, or shift, of light glinting off of Saturn’s moon Titan turns out to drive unexpected reversals in the moon’s atmosphere according to data from NASA’s Cassini spacecraft.

In a paper released in the November 28, 2012 issue of the journal Nature, scientists say in a press release that data from Cassini show evidence for sinking air where upwelling currents were seen earlier in the mission.

“Cassini’s up-close observations are likely the only ones we’ll have in our lifetime of a transition like this in action,” said Nick Teanby, the study’s lead author who is based at the University of Bristol, England, and is a Cassini team associate. “It’s extremely exciting to see such rapid changes on a body that usually changes so slowly and has a ‘year’ that is the equivalent of nearly 30 Earth years.”

Of the eight planets and dozens of moons in our solar system, just Earth, Venus, Mars and Titan have both a solid surface and a substantial atmosphere.

Cassini offers scientists a unique perspective during this change of seasons. The pole experiencing winter is typically pointed away from Earth because of its orbit around Saturn. Cassini provides scientists a platform to watch the atmosphere change over time and study the moon from angles impossible from Earth. It arrived at the ringed planet in 2004. Models of Titan’s atmosphere have predicted changes for two decades but Cassini is just now seeing new circulation patterns arise.

“Understanding Titan’s atmosphere gives us clues for understanding our own complex atmosphere,” said Scott Edgington, Cassini deputy project scientist at NASA’s Jet Propulsion Laboratory, Pasadena, Calif. “Some of the complexity in both places arises from the interplay of atmospheric circulation and chemistry.”

While scientists recently have watched the formation of haze and a vortex over Titan’s south pole, other Cassini instruments, such as the composite infrared spectrometer (CIRS), have gathered data tied more to the circulation and chemistry of Titan’s orangish atmosphere especially at higher altitudes. The CIRS instrument also reveals subtle changes in vertical winds and global circulation. The instrument shows that atmospheric circulation extends about 100 km, or 60 miles, higher than expected. This is important in explaining the orangish tint to Titan’s atmosphere. A haze layer, first detected by Voyager 1, may be a region rich in small haze particles that combine to form larger aggregates that descend deep into the atmosphere giving the moon its characteristic color.

Scientists have narrowed down the atmospheric reversal to about six months near the August 2009 equinox when the Sun was shining directly on Titan’s equator.

“Next, we would expect to see the vortex over the south pole build up,” said Mike Flasar, the CIRS principal investigator at NASA’s Goddard Space Flight Center in Greenbelt, Md. “As that happens, one question is whether the south winter pole will be the identical twin of the north winter pole, or will it have a distinct personality? The most important thing is to be able to keep watching as these changes happen.”

Second image caption: This true color image captured by NASA’S Cassini spacecraft before a distant flyby of Saturn’s moon Titan on June 27, 2012, shows a south polar vortex, or a swirling mass of gas around the pole in the atmosphere. Image Credit: NASA/JPL-Caltech/Space Science Institute

Source: NASA/Jet Propulsion Laboratory

Posted on by John Williams

Swirling Vortex and Mini Moons: Spectacular Views of the Little Things Around Saturn

High-altitude clouds in Titan’s seasonal south polar swirl glow dimly in this image from NASA’s Cassini spacecraft.

With wild storms and a vast ring system, nothing seems small around Saturn. But as NASA’s Cassini spacecraft loops high over Saturn’s poles, scientists are taking time to explore the little things including a swirling vortex, the miniature moon Mimas, and another tiny ovoid moon named Methone.

Titan’s swirling vortex, lower right, glows brightly against the south polar clouds in this new image from NASA’s Cassini spacecraft. Scientists are monitoring the development of the swirling mass of gas to try and understand the weather related to the coming winter to the moon’s south pole. For a color closeup of the vortex, see Titan’s Colorful South Polar Vortex. If you’re more into a moving visualization, check out the vortex in motion.


Cassini acquired the view of the vortex on Titan on August 31, 2012 using a special filter sensitive to light in the near-infrared. Cassini took this image from a distance of about 1.2 million kilometers (750,000 miles) above the south pole of Titan. That’s nearly three times the distance between Earth and the Moon. The smallest detail on this image is about 4 miles across.

“Note the motions and beautifully detailed cloud patterns,” wrote Carolyn Porco, Cassini imaging team lead on the CICLOPS website, “very likely the result of open-cell convection — already visible in this fascinating phenomenon that we on Cassini have been fortunate to capture, for the first time, in the process of being born.”

Methone looks like a tiny gray egg in this image from NASA’s Cassini spacecraft.

Last week, the Cassini imaging team released two stunning images of Saturn. Tiny, egg-shaped Methone (pronounced meh-tho-nee) is barely 3 kilometers (2 miles) across. Cassini discovered this moon in 2004 hanging out between Mimas and Enceladus at just 194,000 km (120,000 miles) above Saturn. From Methone’s smooth surface, Saturn must be a true wonder. Small moons like Methone are generally non-round. Scientists believe they just don’t have the mass to pull themselves together into a round shape. The leading side of Methone is lit in this image and at a distance of just 4,000 km (2,500 miles) the smallest feature that can be seen is about 27 meters (88 feet).

Saturn’s moon Mimas is dwarfed by Saturn and its rings in this spectacular image from NASA’s Cassini spacecraft

Don’t blink or you might miss a tiny dot just to the upper left of Saturn. Mimas is dwarfed not only by Saturn’s rings, but also by the gigantic storms visible in the northern and southern hemisphere’s Mimas is just 396 km (246 miles) across and is the solar system’s 20th largest satellite. The moon could easily fit within the borders of Spain and most western states in the U.S. Cassini took this spectacular image from a distance of 2.4 million kilometers (1.5 million miles) from Saturn.

Source: NASA Jet Propulsion Laboratory and Cassini Imaging Central Laboratory for Operations (CICLOPS)

Posted on by Jason Major

Cassini Discovers Titan’s Glowing Atmosphere

A pair of images from NASA’s Cassini spacecraft show Titan glowing in the dark.

Titan never ceases to amaze. Saturn’s largest moon, it’s wrapped in a complex, multi-layered nitrogen-and-methane atmosphere ten times thicker than Earth’s. It has seasons and weather, as evidenced by the occasional formation of large bright clouds and, more recently, an area of open-cell convection forming over its south pole. Titan even boasts the distinction of being the only other world in the Solar System besides Earth with large amounts of liquid existing on its surface, although there in the form of exotic methane lakes and streams.

We have NASA’s Cassini spacecraft to thank for these discoveries, and now there’s one more for the ceaseless explorer to add to its list: Titan glows in the dark.

Seen above in two versions of the same calibrated raw image, acquired by Cassini on May 7, 2009, Titan hovers in front of a background field of stars which appear as blurred streaks due to the 560 seconds (about 9 1/2 minutes) exposure time and the relative motion of the spacecraft.

The image on the left shows Titan in visible light, receiving reflected sunlight off Saturn itself — “Saturnshine” — while the moon was on the ringed planet’s night side. The image on the right was processed to exclude this reflected light… and yet it still shines. (E pur si candeo?)

Read: Titan’s Surface “the Consistency of Soft, Damp Sand”

The hazy moon’s dim glow — measuring only around a millionth of a watt — comes from not only the top of its atmosphere (which was expected) but also from much deeper within, at altitudes of 300 km (190 miles).

The glow is created by chemical reactions within Titan’s atmosphere, sparked by interactions with charged particles from the Sun and Saturn’s magnetic field.

“It turns out that Titan glows in the dark – though very dimly,” said Robert West, the lead author of a recent study in the journal Geophysical Research Letters and a Cassini imaging team scientist at NASA’s Jet Propulsion Laboratory. “It’s a little like a neon sign, where electrons generated by electrical power bang into neon atoms and cause them to glow. Here we’re looking at light emitted when charged particles bang into nitrogen molecules in Titan’s atmosphere.”

The light is analogous to the airglow seen in Earth’s atmosphere, often photographed by astronauts aboard the ISS.

Still, even taking known sources of external radiation into account, Titan is glowing from within with an as-yet-unexplained light. More energetic cosmic rays may be to blame, penetrating deeper into the moon’s atmosphere, or there could be unexpected chemical reactions or phenomena at work — a little Titanic lightning, perhaps?

“This is exciting because we’ve never seen this at Titan before,” West said. “It tells us that we don’t know all there is to know about Titan and makes it even more mysterious.”

Read more on the Cassini mission page here, and see more images from Cassini on the CICLOPS imaging center site.

Images: NASA/JPL-Caltech/Space Science Institute. Inset image: Titan’s atmosphere and upper-level hydrocarbon haze, seen in June 2012. Color composite by J. Major.

Posted on by Nancy Atkinson

Titan’s Surface the “Consistency of Soft, Damp Sand”

Artist depiction of Huygens landing on Titan. Credit: ESA

Artist concept of the Huygens probe landing on the surface of Titan. Credit: ESA

Even though the Huygens probe landed on Titan back in 2005 and transmitted data for only about 90 minutes after touchdown, scientists are still able to eke information out about Titan from the mission, squeezing all they can from the data. The latest information comes from reconstructing the way the probe landed, and an international group of scientists say the probe “bounced, slid and wobbled” after touching down on Saturn’s moon, which provides insight into the nature of the Titan’s surface.

“A spike in the acceleration data suggests that during the first wobble, the probe likely encountered a pebble protruding by around 2 cm from the surface of Titan, and may have even pushed it into the ground, suggesting that the surface had a consistency of soft, damp sand,” describes Dr. Stefan Schröder of the Max Planck Institute for Solar System Research, lead author of a paper recently published in Planetary and Space Science.

An animation of the landing is below.

Schröder and his team were able to reconstruct the landing by analyzing data from different instruments that were active during the impact, and in particular they looked for changes in the acceleration experienced by the probe.

The instrument data were compared with results from computer simulations and a drop test using a model of Huygens designed to replicate the landing.

The scientists think that Huygens landed in something similar to a flood plain on Earth, but that it was dry at the time. The analysis reveals that, on first contact with Titan’s surface, Huygens dug a hole 12 cm deep, before bouncing out onto a flat surface.

The probe, tilted by about 10 degrees in the direction of motion, then slid 30–40 cm across the surface.

It slowed due to friction with the surface and, upon coming to its final resting place, wobbled back and forth five times. Motion subsided about 10 seconds after touchdown.

Earlier studies of data from Huygens determined the surface of Titan to be quite soft. The new study goes one step farther, the team said, to demonstrate that if something put little pressure on the surface, the surface was hard, but if an object put more pressure on the surface, it sank in significantly.

“It is like snow that has been frozen on top,” said Erich Karkoschka, a co-author at the University of Arizona, Tucson. “If you walk carefully, you can walk as on a solid surface, but if you step on the snow a little too hard, you break in very deeply.”

Had the probe impacted a wet, mud-like substance, its instruments would have recorded a “splat” with no further indication of bouncing or sliding. The surface must have therefore been soft enough to allow the probe to make a sizable depression, but hard enough to support Huygens rocking back and forth.

This raw image was returned by the Descent Imager/Spectral Radiometer camera onboard the European Space Agency’s Huygens probe after the probe descended through the atmosphere of Titan. It shows the surface of Titan with ice blocks strewn around. Credit: ESA/NASA/University of Arizona

“We also see in the Huygens landing data evidence of a ‘fluffy’ dust-like material – most likely organic aerosols that are known to drizzle out of the Titan atmosphere – being thrown up into the atmosphere and suspended there for around four seconds after the impact,” said Schröder.

Since the dust was easily lifted, it was most likely dry, suggesting that there had not been any rain of liquid ethane or methane for some time prior to the landing.

“You don’t get rain very often on Titan,” said Karkoschka, explaining that heavy downpours of liquid methane may occur decades or centuries apart. “When they do occur, they carve the channels we see in the pictures Huygens recorded as it approached the surface. The top layer at the landing site was completely dry, suggesting it hadn’t rained in a long time,” he added.

Karkoschka said that when Huygens landed, its downward-shining lamp warmed up the ground and caused methane to evaporate,” Karkoschka explained. “That tells us that just below the surface, the ground probably was wet.”

It has been suggested in earlier studies that the Huygens probe landed near the edge of one of Titan’s hydrocarbon lakes. Several hundred lakes and seas have been observed with the Cassini orbiter’s radar instruments, but with surface temperatures of minus 179 degrees Celsius (minus 290 degrees Fahrenheit), Titan does not have bodies of water. Instead, liquid hydrocarbons in the form of methane and ethane are present on the moon’s surface, with complex carbons making up dunes and other features on the surface.

Source: ESA

Posted on by Jason Major

Pictures From T-86: Cassini’s Latest Flyby of Titan

On September 26-27 Cassini executed its latest flyby of Titan, T-86, coming within 594 miles (956 km) of the cloud-covered moon in order to measure the effects of the Sun’s energy on its dense atmosphere and determine its variations at different altitudes.

The image above was captured as Cassini approached Titan from its night side, traveling about 13,000 mph (5.9 km/s). It’s a color-composite made from three separate raw images acquired in red, green and blue visible light filters.

Titan’s upper-level hydrocarbon haze is easily visible as a blue-green “shell” above its orange-colored clouds.

Cassini captured this image as it approached Titan’s sunlit limb, grabbing a better view of the upper haze. Some banding can be seen in its highest reaches.

The haze is the result of UV light from the Sun breaking down nitrogen and methane in Titan’s atmosphere, forming hydrocarbons that rise up and collect at altitudes of 300-400 kilometers. The sea-green coloration is a denser photochemical layer that extends upwards from about 200 km altitude.

In this image, made from data acquired on Sept. 27, Titan’s south polar vortex can be made out just within the southern terminator. The vortex is a relatively new feature in Titan’s atmosphere, first spotted earlier this year. It’s thought that it’s a region of open-cell convection forming above the moon’s pole, a result of the approach of winter to Titan’s southern half.

Read: Cassini Spots Surprising Swirls Above Titan’s South Pole

This T-86 flyby was was one of a handful of opportunities to profile Titan’s ionosphere from the outermost edge of Titan’s atmosphere. In addition Cassini was able to look for any changes to Ligeia Mare, a methane lake last observed in spring of 2007.

Now that Titan has been under scrutiny for a full year of Saturn’s seasons — which lasts 29.7 Earth-years — astronomers now know that varying amounts of solar radiation can drastically change situations both within Saturn’s atmosphere and on its surface.

“As with Earth, conditions on Titan change with its seasons. We can see differences in atmospheric temperatures, chemical composition and circulation patterns, especially at the poles,” said Dr. Athena Coustenis from the Paris-Meudon Observatory in France. “For example, hydrocarbon lakes form around the north polar region during winter due to colder temperatures and condensation. Also, a haze layer surrounding Titan at the northern pole is significantly reduced during the equinox because of the atmospheric circulation patterns. This is all very surprising because we didn’t expect to find any such rapid changes, especially in the deeper layers of the atmosphere.”

“It’s amazing to think that the Sun still dominates over other energy sources even as far out as Titan, over 1.5 billion kilometres from us.”
– Dr. Athena Coustenis, Paris-Meudon Observatory

The image above, acquired on Sept. 28, was added to this post on Oct. 1. It was taken from a distance of  649,825 miles (1,045,792 kilometers.)

Cassini’s next targeted approach to Titan — T-87 — will occur on November 13.

Get more news from the Cassini mission here.

Image credits: NASA/JPL/Space Science Institute. All color composites by Jason Major. Images have not been validated or calibrated by the SSI team.

 

(Do you love the Cassini mission as much as we do? Vote on your favorite Cassini “Shining Moment” here, in honor of the 15th anniversary of Cassini’s launch on October 15! Amazing to think it’s already been 15 years — 8 of those in orbit around Saturn!)

Posted on by Fraser Cain

Weekly Space Hangout – Sept. 27, 2012

This was an action-packed episode of the Weekly Space Hangout. Lots of stories, very little time.

Participants: Mike Wall, Alan Boyle, Ian O’Neill, Nancy Atkinson, Jason Major

Host: Fraser Cain

Want to watch us record the show live? Point your browser at next week’s event page to put the recording right into your calendar.

Posted on by Nancy Atkinson

Paddleboat Mission to Titan Proposed

Three concepts for the TALISE boat mission to Titan: screw propelled (left), paddle wheels (center) and inflatable wheels (right). Credit: Urdampilleta, et al.

Is sending a boat to Titan an outlandish idea? Maybe, said a group of European scientists and engineers, but they’re working on a plan. The Titan Lake In-situ Sampling Propelled Explorer (TALISE) proposes a sending an instrument-laden boat-probe to Saturn’s largest moon that could be propelled by paddles, inflatable wheels or screws. The probe would land in the middle of Ligeia Mare – Titan’s biggest lake, near the moon’s north pole — then set sail for the coast, taking scientific measurements along the way.

“The main innovation in TALISE is the propulsion system,” says Igone Urdampilleta from SENER, an engineering company in Spain and a member of the TALISE team. “This allows the probe to move, under control, from the landing site in the lake, to the closest shore. The displacement capability would achieve the obtaining of liquid and solid samples from several scientific interesting locations on Titan’s surface such as the landing place, along the route towards the shore and finally at the shoreline.”

In a presentation at the European Planetary Science Congress on September 27, 2012, the TALISE team says that since Titan has a thick atmosphere, a diameter between that of Earth and the planet Mercury, and a network of seas, lakes and rivers, it is in many respects more like a planet than a moon.

And it’s time to go there and do a little in-situ science. The principle objective of the mission would be to characterize Titan’s environment and the chemical composition of the lakes and terrain.

While the Cassini-Huygens mission landed the Huygens probe on Titan in 2005, it transmitted data for only about 90 minutes after touchdown. The TALISE mission would last six months to a year.

Images from the Cassini mission show river networks draining into the lakes in Titan’s north polar region. Credit: NASA/JPL/USGS

The Cassini orbiter has confirmed that lakes, seas and rivers of liquid hydrocarbons cover much of the Titan’s northern hemisphere, and these hydrocarbons may rain down on the surface, forming the frigid liquid bodies. With surface temperature at -178 degrees Celsius (-289 degrees Fahrenheit), Titan’s environment is too cold for life as we may know it, but its environment, rich in the building blocks of life, is of great interest to astrobiologists, the team said.

“The chemical composition of the lakes of Titan is still not well determined,” the TALISE team wrote in their abstract. “The detection of other compounds and the investigation of influence of both, photochemistry and the atmosphere on the chemical composition of liquids of Titan lakes remain challenging in the absence of in situ measurements. Therefore, it is next step to understand the Titan lakes environment, its relationship with the climate behavior, the surrounding solid substrate and analyze the organic inventory including the possibility of prebiotic compounds.”

The actual configuration of the boat is still under consideration, and they are considering various in-situ propulsion methods through the liquid hydrocarbon seas. In addition to paddle wheels, screw propulsion and inflatable wheels, they are also looking at tank wheels, air propeller, liquid propeller and a hovercraft design.

The TALISE concept is being developed as a partnership between SENER and the Centro de Astrobiología in Madrid, Spain, and the mission is still in the very early stages of feasibility studies and preliminary mission architecture design, but they are hoping to be ready for a future space science mission call for proposals.

Sources: EPSC, TALISE team abstract

Posted on by John Williams

Changing Hues Signal Transition of Seasons at Saturn

The giant moon Titan passes in front of Saturn in this natural-color, wide-angle view from NASA’s Cassini spacecraft. Image Credit: NASA/JPL-Caltech/SSI

[SPOILER ALERT: Viewing these images will force you to change your computer wallpaper]

Here on Earth, it’s almost time for the burst of fall color that signals the change of seasons in the Northern Hemisphere. Saturn’s color too is transforming subtly as the gas giant slips into a Saturnian spring and autumn as seen in this series of true-color images from NASA’s Cassini spacecraft.

Titan, a moon larger than the planet Mercury, hangs before the rings and changing colors of Saturn in the first of four spectacular images release by NASA and the Cassini Imaging Central Laboratory for Operations (CICLOPS).

“For no other reason than that they are gorgeous, the Cassini imaging team is releasing today a set of fabulous images of Saturn and Titan…in living color…for your day-dreaming enjoyment,” said Carolyn Porco, Cassini imaging team lead based at the Space Science Institute in Boulder, Colordo, in an email blast.

When Cassini arrived at Saturn eight years ago, the planet’s northern hemisphere, locked in winter, showed azure blue. Now as winter passes to the southern hemisphere, the colors are reversing as the blue fades from the north and rises in the south.

“Note that our presence at Saturn for the last eight years has made possible the sighting of subtle changes with time, and one such change is obvious here,” Porco said. “As the seasons have advanced, and spring has come to the north and autumn to the south throughout the Saturn system, the azure blue in the northern winter Saturnian hemisphere that greeted Cassini upon its arrival in 2004 is now fading; and it is now the southern hemisphere, in its approach to winter, that is taking on a bluish hue.”

Scientists believe that the increasing blue color in the south likely is due to the increasing intensity of ultraviolet light from the Sun which produces the haze. Methane in the atmosphere also absorbs light toward the red end of the spectrum while reflecting blue light. This view looks from just above the ring plane with the Sun shining from above casting broad shadows on the colorful clouds of Saturn. The image was taken on May 6, 2012 from about 778,000 kilometers (483,000 miles) from Titan.

Some of the views, including this image of a vortex at Titan’s south pole are only possible because of a newly tilted, or inclined, orbit that takes Cassini high over the poles of Saturn and its moons. Scientists first noticed the detached mass of clouds over the south pole in March. The swirling mass of the vortex stands out clearly against the golden cloud deck surrounding Titan.

The recently formed south polar vortex stands out against Titan in this natural-color view from NASA’s Cassini spacecraft. Image Credit: NASA/JPL-Caltech/SSI

Sunlight scattering through Titan’s atmosphere forms a ring of color as NASA’s Cassini spacecraft cruises along the night side of Saturn’s largest moon. Image Credit: NASA/JPL-Caltech/SSI

A glowing hint of the polar vortex shows in this image looking toward the night-time, Saturn-facing side of Titan. Sunlight scattering through Titan’s atmosphere forms the ring of color in this image taken about 216,000 kilometers (134,000 miles) from Titan.

Saturn’s rings cut colorful Titan in half in this image from NASA’s Cassini spacecraft. Image Credit: NASA/JPL-Caltech/SSI

The rings obscure Titan in the final image of the quartet. The image is taken from just above the northern, sunlit side of the ring plane. Saturn’s shadow cast along the rings create the dark swath in the center of the image but if you look close, you can see a tiny sliver of Titan through the Cassini Division, the largest gap in Saturn’s wide rings.

“Cassini has been in orbit now for the last eight years, and despite the fact that we can’t know exactly what the next five years will show us, we can be certain that whatever it is will be wondrous,” said Porco.

About the author: John Williams is owner of TerraZoom, a Colorado-based web development shop specializing in web mapping and online image zooms. He also writes the award-winning blog, StarryCritters, an interactive site devoted to looking at images from NASA’s Great Observatories and other sources in a different way. A former contributing editor for Final Frontier, his work has appeared in the Planetary Society Blog, Air & Space Smithsonian, Astronomy, Earth, MX Developer’s Journal, The Kansas City Star and many other newspapers and magazines.

Posted on by Jason Major

Surprising Swirls Above Titan’s South Pole

View of Titan's South Pole, showing a vortex. Credit: NASA

Thanks to Cassini’s new vantage point granted by its inclined orbit researchers have gotten a new look at the south pole of Titan, Saturn’s largest moon. What they’ve recently discovered is a swirling vortex of gas forming over the moon’s pole, likely the result of the approach of winter on Titan’s southern hemisphere.

What we’re seeing here is thought to be an open cell convection process in Titan’s upper atmosphere. In open cells, air sinks in the center of the cell and rises at the edge, forming clouds at cell edges. However, because the scientists can’t see the layer underneath the layer visible in these new images, they don’t know what other mechanisms may be at work.

A stable atmospheric event that’s found here on Earth as well, open cell convection can be compared to the action of boiling water.

Titan has already been seen to have a thicker area of high-altitude haze over its north pole, and as autumn progresses toward winter in Titan’s south during the course of Saturn’s 29.7-year-long orbit this may very well be the beginnings of a southern polar hood.

An animation of this southern vortex can be found here.

“We suspect that this maelstrom, clearly forming now over the south pole and spinning more than forty times faster than the moon’s solid body, may be a harbinger of what will ultimately become a south polar hood as autumn there turns to winter.  Of course, only time will tell.”

– Carolyn Porco, Cassini Imaging Team Leader

Discoveries like this are prime examples of why it was so important for Cassini to have an extended, long-duration mission around Saturn, so that seasonal changes in the planet and moons could be closely observed. New seasons bring new surprises!

The southern vortex structure was also captured in raw images acquired by Cassini on June 28. A color-composite made from three of those raw images is below (the vortex can be seen at center just right of the terminator):

You can find more images from Cassini on the CICLOPS Imaging Team site.

Image credits: NASA/JPL/Space Science Institute. Bottom RGB composite by Jason Major.

Posted on by Jason Major

Titan’s Tides Suggest a Subsurface Sea

Saturn’s hazy Titan is now on the short list of moons that likely harbor a subsurface ocean of water, based on new findings from NASA’s Cassini spacecraft.

As Titan travels around Saturn during its 16-day elliptical orbits, it gets rhythmically squeezed by the gravitational pull of the giant planet — an effect known as tidal flexing (see video below.) If the moon were mostly composed of rock, the flexing would be in the neighborhood of around 3 feet (1 meter.) But based on measurements taken by the Cassini spacecraft, which has been orbiting Saturn since 2004, Titan exhibits much more intense flexing — ten times more, in fact, as much as 30 feet (10 meters) — indicating that it’s not entirely solid at all.

Instead, Cassini scientists estimate that there’s a moon-wide ocean of liquid water beneath the frozen crust of Titan, possibly sandwiched between layers of ice or rock.

“Short of being able to drill on Titan’s surface, the gravity measurements provide the best data we have of Titan’s internal structure.”

– Sami Asmar, Cassini team member at JPL

“Cassini’s detection of large tides on Titan leads to the almost inescapable conclusion that there is a hidden ocean at depth,” said Luciano Iess, the paper’s lead author and a Cassini team member at the Sapienza University of Rome, Italy. “The search for water is an important goal in solar system exploration, and now we’ve spotted another place where it is abundant.”

Although liquid water is a necessity for the development of life, the presence of it alone does not guarantee that alien organisms are swimming around in a Titanic underground ocean. It’s thought that water must be in contact with rock in order to create the necessary building blocks of life, and as yet it’s not known what situations may exist around Titan’s inner sea. But the presence of such an ocean — possibly containing trace amounts of ammonia — would help explain how methane gets replenished into the moon’s thick atmosphere.

“The presence of a liquid water layer in Titan is important because we want to understand how methane is stored in Titan’s interior and how it may outgas to the surface,” said Jonathan Lunine, a Cassini team member at Cornell University, Ithaca, N.Y. “This is important because everything that is unique about Titan derives from the presence of abundant methane, yet the methane in the atmosphere is unstable and will be destroyed on geologically short timescales.”

The team’s paper appears in today’s edition of the journal Science. Read more on the Cassini mission site here.

Top image: artist’s concept showing a possible scenario for the internal structure of Titan. (A. Tavani). Side image: An RGB-composite color image of Titan and Dione in front of Saturn’s face and rings, made from Cassini images acquired on May 21, 2011. (NASA/JPL/SSI. Composite by J. Major.)